Biomedical Engineering Reference
In-Depth Information
sizes, shape and surface roughness of the scaffolds are known to
affect cellular adhesion, proliferation and phenotype. Additionally,
the surface energy may play a role in attracting particular proteins
to the bioceramic surface and, in turn, this will affect the cells affinity
to the material. More to the point, cells are exceedingly sensitive to
the chemical composition and their bone-forming functions can
be dependent on grain morphology of the scaffolds. For example,
osteoblast functions were found to increase on nanodimensional
fibers if compared to nanodimensional spheres because the former
more closely approximated the shape of biological apatite in bones
[701]. Besides, a significantly higher osteoblast proliferation on
HA bioceramics sintered at 1200°C as compared to that on HA
bioceramics sintered at 800°C and 1000°C was reported [702].
Thus, to meet the tissue engineering requirements, much attention
is devoted to further improvements of calcium orthophosphate
bioceramics [703]. From the chemical point of view, the developments
include synthesis of novel ion-substituted calcium orthophosphates
[8-38]. From the material point of view, the major research topics
include nanodimensional and nanocrystalline structures [704-
708] and Chapter 3, organic-inorganic biocomposites and hybrid
biomaterials (Chapter 6), fibers, whiskers and filaments [709-722],
micro- and nano-sized spheres and beads [722-737], micro- and
nano-sized tubes [738-740], porous 3D scaffolds made of ACP [462,
598], TCP [432-435], HA [176, 397, 398, 436, 438, 485, 688, 741-
747] and various biphasic formulations [484, 700, 733, 748-752],
structures with graded porosity [375, 411, 482, 484, 578-585,
588] and hierarchically organized ones [753, 754]. Furthermore,
an addition of defects through an intensive milling [755, 756] or
their removal by a thermal treatment [757] can be used to modify
a chemical reactivity of calcium orthophosphates. Besides, more
attention should be paid to a crystallographically aligned calcium
orthophosphate bioceramics [758].
There are three principal therapeutic strategies for treating
diseased or injured tissues in patients: (i) implantation of freshly
isolated or cultured cells; (ii) implantation of tissues assembled
in
vitro
tissue regeneration. For
cellular implantation, individual cells or small cellular aggregates
from the patient or a donor are either injected into the damaged tissue
directly or are combined with a degradable scaffold
from cells and scaffolds; (iii)
in situ
and then
implanted. For tissue implantation, a complete 3D tissue is grown
in vitro
in
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